In the related art, there is a known suture instrument for suturing tissue or the like inside a body (see PTL 1).
This suture instrument has two openable/closable gripping members at the tip of an elongated shaft member that is inserted into the body of a patient. A passing mechanism that passes the suture needle is provided in the gripping members, and by pinching the object to be sutured with the two gripping members in the state in which the suture needle, to which a suture thread is attached, is held by one of the gripping members, the suture needle is made to penetrate the object to be sutured, and the object to be sutured is sutured by alternately passing the suture needle between the two gripping members by means of the passing mechanism.
The passing mechanism is provided in each of the gripping members and includes a fitting hole portion that holds, in a fitting manner, the suture needle in the opening/closing direction of the gripping members, and a plate-shaped holding member that is movable in a direction intersecting the opening/closing direction (the longitudinal direction of the gripping member). The holding member is provided with a slit whose width varies along the moving direction, and the suture needle is provided with two narrow portions which are apart from each other in the longitudinal direction of the suture needle and which can be inserted into a narrow portion of the slit.
By moving the holding member to the distal end of the gripping member so that the suture needle is positioned in the narrow portion of the slit, the suture needle disposed so as to be inserted in the fitting hole portion can be held in the gripping members so that the narrow portion is engaged with the slit, and the suture needle does not fall out from the fitting hole portion. On the other hand, by moving the holding member to the proximal end of the gripping members so that the suture needle is positioned in a wide portion of the slit, the narrow portion and the slit may be disengaged, allowing the suture needle to be removed from the fitting hole portion. By performing these operations and the opening/closing operation of the gripping members, the suture needle can be passed between the gripping members.